In many environments it is necessary to temporarily hold and clamp parts together while other operations, such as drilling and riveting operations, are performed. For example, tack fasteners are widely used in the aircraft industry to temporarily attach the sheets of metal used to form the skin of an aircraft to the flanges of supporting structural elements, such as stringers and frames. Since it is time consuming and sometimes difficult (and, therefore, expensive) to temporarily fasten parts together using conventional mechanical devices, such as nuts and bolts, tack fasteners have been developed to avoid these problems. While various tack fasteners have been developed, those that require access to only one side of the parts to be fastened together are preferred, at least in the aircraft industry.
In addition to being undesirably complex, one disadvantage of prior tack fasteners, particularly those used in the aircraft industry, resides mainly in the inability to provide the high compression forces that are occasionally needed to pull parts together. In the past, this disadvantage has been overcome by utilizing nuts and bolts in regions where abnormally high compression forces are required and/or using a large number of closely spaced tack fasteners. Obviously, both approaches have disadvantages. The installation of nuts and bolts is time consuming and, frequently, requires the services of two employees, rather than a single employee. The use of large numbers of tack fasteners requires the creation of additional tack fastener holes and is particularly undesirable when tack fasteners: (a) must be removed after permanent fasteners are installed in other holes; (b) the tack fastener holes drilled to a larger size; and, (c) permanent fasteners installed in the enlarged holes.
Another disadvantage of prior tack fasteners, particularly those that require access to only one side of the parts to be fastened together, relates to their difficulty of installation. Specifically, many prior tack fasteners have a barrel-like housing and parallel tangs that project outwardly from one end of the housing. The housing and components mounted in the housing coact together to pull the tangs into the housing when the housing and the components are rotated with respect to one another. The fastener is installed by pushing the tangs through aligned holes in the parts to be fastened together. After enlarged tips located at the ends of the tangs clear the blind side of the parts, the housing and the components are rotated to spread the tangs and, then, pull the tangs into the housing. Because the tangs are free to rotate with respect to the holes in the parts, housing and component rotation requires the use of both hands of the installer, at least until the parts are drawn together with an adequate amount of clamp up force.
The present invention is directed to providing a new and improved tack fastener that avoids the foregoing and other disadvantages of prior tack fasteners.